Examination of mitochondria- and inflammasome-mediated mechanisms of clozapine-induced myocarditis using patient-derived iPSC cardiomyocytes.

Clozapine is the only approved pharmacotherapy for treatment-resistant schizophrenia. However, widespread utilization of clozapine is constrained due to the potential for severe adverse effects, including myocarditis. Multiple mechanisms have been suggested to account for the cardiotoxic effects of clozapine, yet these investigations have not used cells derived from clozapine treated patients. In this study, cardiomyocytes that were derived from induced pluripotent stem cells generated from four patients with treatment-resistant schizophrenia with (n = 2) and without (n = 2) a history of clozapine-induced myocarditis were used to assess mitochondria- and NLRP3 inflammasome-mediated mechanisms of this severe adverse drug reaction. We found treatment of cardiomyocytes with a physiologically-relevant dose (2.8 µM) of clozapine for 24 h: (1) induced cardiac dysfunction, increased cytotoxicity, and apoptosis, (2) induced oxidative stress by elevating the level of reactive oxygen species and mitochondrial fragmentation, and (3) elevated levels of proinflammatory cytokines and activated the NLRP3 inflammasome. These effects were more pronounced in cardiomyocytes derived from individuals with a history of clozapine-induced myocarditis. Furthermore, pharmacological targeting of the mitochondria (elamipretide) and inflammasome (ustekinumab) attenuated these clozapine-induced cardiotoxic effects. Collectively, these results suggest a mitochondria- and NLRP3 inflammasome-mediated mechanism in the development of myocarditis associated with clozapine and support further evaluation of therapeutics that target mitochondria and NLRP3 signaling.